Frequent biofilm production by Staphylococcus epidermidis causing infection in pets or colonizing veterinary staff

Aim: To characterize biofilm production by Staphylococcus epidermidis isolates causing infection in pets or colonizing veterinary staff. Methods: The study collection comprised 129 S. epidermidis isolates, from nasal colonization of vet-erinary staff (n = 112) and causing infection in cats and dogs (n = 17). The capacity to produce biofilm was evaluated by the Crystal Violet (CV) method, performed in flat-bottom 96-well polystyrene plates and biofilm production was categorized (as strong, moderate or weak) according to specific ranges of 570 nm optical density. The biofilm producer S. epidermidis RP62A was used as control in each assay. Biofilm-associated genes icaAD and aap were screened by PCR.Results: Amongst thehumancommensal isolates, the CV method enabled the identification of 66/112 (58.9 %) biofilm producers, of which 34/66 (51.5 %) were strong or moderate producers. In the group of pet infection isolates, 16/17 isolates (94.1 %) produced biofilm, of which 12/16 (75.0%) were strong or moderate producers. The majority of the isolates carried icaAD and/or aap genes. The genotype icaAD-aap- was associated with non-biofilm production whereas genotype icaAD+aap+ was linked to strong biofilm production. No correlation was found between any biofilm producing phenotype and the genotypes icaAD+aap-icaAD-aap+.Conclusion: These results evidence a high frequency of biofilm production by S. epidermidis either causing infection in pets or colonizing humans in close contact with them. The findings also highlight the importance of biofilm-associated genes other than ica in the biofilm phenotype.